Dr Arvind Madan, the head of NHS primary care has written to GPs (on Friday 7 July), warning them that now is a crucial time to look out for people, especially children, who are struggling to recover from the spate of incidents.

"Children and young people experiencing symptoms which may indicate PTSD might think differently about themselves or other people," the letter warns.

"Those suffering trauma might also experience overwhelming shame, sadness or fear, or avoid situations which remind them of the event."

But it's not just doctors who will want to look out for these signs. HuffPost UK has spoken to the charity Victim Support (VS), to get advice for parents who are concerned about their children.

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Charlotte Cross, specialist case worker in Victim Support's Homicide Service, said now is a vital time for parents to watch out for signs of PTSD as it can take weeks and even months for the full extent of someone's trauma to surface.

"Sadly, in the last few weeks thousands of children and young people – who are still trying to work out how to process their response to normal day-to-day life - have experienced traumatic events that few adults could cope with," she said.

"It can be heartbreaking for loved ones to stand by and watch the fallout as a young person tries to process the kinds of horrors that many have witnessed at Manchester Arena, at Grenfell Tower or at London Bridge.

"We also know that you don't have to have been at an event to suffer. Many young people will have been terribly affected in the aftermath of recent events, having seen their close friends and family suffer unimaginable pain.

"For all of these young people the world will never be quite the same. But with the right support they can re-build their shattered lives and move forward to a positive future."

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A boy writes a tributes near the scene of the 19 June van attack on pedestrians, in the Finsbury Park area of north London.

According to Cross, parents who are concerned about their children after a traumatic event should watch out for the following signs of PTSD:

1. Retreating

Having been confronted full force with a world they don't feel able to deal with, many young people will simply retreat.

2. Heightened Anxiety

Many people who have experienced traumatic incidents experience heightened and constant feelings of anxiety. This can be extremely debilitating leaving those suffering feeling overwhelmed by daily tasks, prone to panic attacks and even suffering physical symptoms, such as regular diarrhoea.

3. Obsessive Online Trawling

In an attempt to "make sense" of their experience some victims will obsessively trawl the internet for videos, news reports and updates. This can be especially prevalent in younger victims already immersed in the online world.

Each time that a young person finds a video or harrowing first person account related to the event they experienced they are effectively "re-traumatising" themselves.

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4. Not Eating Or Sleeping

Our body reacts to trauma by going into fight or flight mode. In a state of "high alert" our bodies can reject the idea of food or sleep and over time this can become ingrained behaviour.

5. Experiencing Flashbacks

People who have witnessed or experienced a deeply traumatic incident can suffer "flashbacks".

The distressing thing about flashbacks is that they can be brought on unexpectedly at any time by something that to anyone else might seem harmless.

The smell of a BBQ, an unexpected loud noise, someone shouting – can all trigger frightening emotions and take a victim right back to the event.

6. Seeming "Fine"

One of the most distressing reactions to a traumatic event can be when a young person seems totally unaffected. Often this means that a victim has simply "buried" their emotions.

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A girl draws on a memorial set against railings in tribute to the victims and the missing from the Grenfell Tower block fire close to the scene in North Kensington, west London.

What can parents do to help their child after a traumatic incident?

According to Victim Support's research into the effects of terrorism on victims, 94% of survivors will at some point suffer effects such as problems with sleeping, anxiety, anger and flashbacks, and the vast majority need emotional and psychological help.

So, Cross advises that the best thing you can do is to regularly remind your child that you are there for them and that help does exist.

She adds that you can also take the following steps:

1. Create A Support Network For Your Child

Sometimes children and especially teens can find it hardest to talk to those they are closest to.

If a family has suffered an event together young people may feel worried about making them relive the event by talking it through.

Help them identify two or three trusted adults they can talk to – that might be a family friend, a teacher or a relative. The fact that they are one step removed from the situation can help strip some of the emotion away and enable your young person to open up.

2. Don't Hound Your Child

When you're worried about someone, your natural instinct is to reach out, but if you hound your young person you can inadvertently push them away.

Let them know that you are there, and remind them on a regular basis, but let them come to you in their own time and on their own terms.

3. Create Opportunities To Talk

A lot of young people find it easier to talk when the intensity of a situation is "dialled down".

Rather than pulling them aside to chat to them face-to-face and one-to-one, strike up conversation while you're in the car (and they're not having to make direct eye contact) or do something active together – go for a walk, run or a kick about in the park.

Doing something together not only reassures them that they are valued but can help "loosen them up" to chat about their emotions.

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4. Monitor Their Online Use

Don't allow your child to get "lost" in the online world as they seek solace from the real world.

Be strict about limiting their access and give them opportunities to lose themselves in other activities. Exercise is a great way of getting rid of pent up anger and anxiety.

5. Provide Context

A child or young person who has experienced a deeply traumatic incident or the horrors of a terrorist attack can lose their faith in the world.

Help them put the event into context and regain their trust by sharing stories of humanity and by giving them anecdotal evidence of kindnesses you've seen or heard about as you go about your daily life.

6. Re-Build Their Confidence

Help your young person re-gain their confidence by setting them small challenges.

Every time they successfully complete one, the sense of achievement they feel is something they can latch onto next time they are feeling overwhelmed by their emotions.

Challenges can be anything from running a 5k race to meeting their friends on their own in town for an hour or even holding a mini fundraising event.

7. Signpost Professional Help

According to Victim Support's research into the impact of terrorism, over three quarters (79%) of victims will require emotional and psychological support.

Regularly remind your child that help is there and can be accessed whenever they are ready – whether that is weeks or even years after the attack.

At Victim Support specially trained case workers provide free and confidential emotional and practical support for as long as someone needs us. Anyone affected by a terrorist attack, traumatic incident or crime can contact VS's Supportline on 08 08 16 89111.

And remember that by just being there and showing that you care, you are helping already.

Victim Support are fundraising to ensure they can continue to provide support for victims of terrorist attacks. If you would like to contribute you can do so here.